Display apparatus, control method thereof, and program

ABSTRACT

A display apparatus includes a USB connector used to connect an external device so as to be able to communicate with that device. The display apparatus also includes a CPU which controls to make a display based on data received from the external device with which a communication connection is established via the USB connector. The CPU acquires class information indicating a class of the external device, the communication connection of which is established. When the communication connection with the external device is disconnected, if the acquired class information indicates a predetermined class, the CPU controls to continue the display based on the received data, and if the class information does not indicate the predetermined class, the CPU controls to end the display.

This application is a continuation of application Ser. No. 13/281,543,filed Oct. 26, 2011, now U.S. Pat. No. 8,078,767, issued Dec. 13, 2011,which is a divisional of application Ser. No. 12/545,270, filed Aug. 21,2009, which is a continuation of PCT Application No. PCT/JP/2009/055831,filed Mar. 24, 2009.

TECHNICAL FIELD

The present invention relates to a display apparatus, a control methodthereof, and a program.

BACKGROUND ART

Conventionally, a display apparatus such as a projector is connected tovarious devices via, for example, USB (Universal Serial Bus), anddisplays image data transmitted from these connected devices. Variousdevices connected to the display apparatus include a semiconductormemory device such as a flash memory device, a PC (Personal Computer), adigital still camera (to be referred to as a “digital camera”hereinafter), and the like.

A case will be explained first with reference to FIGS. 11A to 13Cwherein a flash memory as a semiconductor memory device is connected toa projector as a display apparatus, and image data stored in that flashmemory is displayed on the projector. FIG. 11A is a schematic viewshowing an overview when a flash memory 93 is connected to aconventional projector 91 to display an image. FIG. 11B is a schematicview showing details of a control panel 9101. FIG. 12 is a sequencechart showing the operation sequence executed when the flash memory 93is connected to the projector 91 to display an image. FIGS. 13A to 13Care schematic views exemplifying images to be projected by the projector91 onto a screen 92.

As shown in FIG. 11A, the projector 91 has the control panel 9101 and aUSB connector 9102. As shown in FIG. 11B, the control panel 9101 has anup arrow button 9011, left arrow button 9012, down arrow button 9013,right arrow button 9014, enter button 9015, input button 9016, and powerbutton 9017. The projector 91 accepts operation instructions from theuser from various buttons on the control panel 9101. The USB connector9102 receives the flash memory 93 having a USB connection terminal. Thisflash memory 93 stores image data to be displayed by the projector 91.By the user plugging the flash memory 93 into the USB connector 9102 andoperating the control panel 9101, he or she can browse image data storedin the flash memory 93 as an image 921 on the screen 92.

The operation sequence among the user, flash memory 93, and projector 91will be described below. Assume that the projector 91 is powered, andthe flash memory 93 is not connected to the projector 91 in an advancestate. As shown in FIG. 12, the operation sequence by the user, flashmemory 93, and projector 91 mainly include steps S200 to S210 which areexecuted in turn. In step S200, the projector 91 displays a connectionrequest window that requests the user to connect the flash memory 93 tothe USB connector 9102 by projecting that window on the screen 92. Theconnection request window in step S200 displays a message that promptsthe user to connect the flash memory 93 as a USB device, as shown inFIG. 13A.

In step S201, the user connects the flash memory 93 to the USB connector9102. In step S202, a USB communication is established based on the USBstandard between the projector 91 and flash memory 93 which arephysically connected via the USB connector 102. In this case, theprojector 91 recognizes the flash memory 93 as Mass Storage Class basedon the USB standard.

In step S203, the projector 91 reads directory entry information storedin the flash memory 93. In step S204, the projector 91 displays a fileselection window that prompts the user to select an image file to bedisplayed by projecting that window on the screen 92. The file selectionwindow in step S204 is as shown in FIG. 13B, and is a window thatdisplays a file name list of image files stored in the flash memory 93,and a cursor used to select them.

In step S205, the user who confirmed the aforementioned file selectionwindow selects an image file to be displayed by operating the controlpanel 9101 and issues a display instruction to the projector 91. Forexample, in step S205 the user gives an instruction to move the cursorby pressing the up or down arrow button 9011 or 9013 on the controlpanel 9101, and issues a display instruction of an image file selectedby the cursor by pressing the enter button 9015.

In step S206, the projector 91 reads data of the image file designatedin step S205 from the flash memory 93. In step S207, the projector 91displays an image based on the image file read in step S206 byprojecting that image on the screen 92. As the image displayed in stepS207, image data of a landscape or the like captured using a digitalcamera is stored in advance in the flash memory 93, as shown in FIG.13C.

In step S208, the user issues a display end instruction to the projector91 by operating the control panel 9101. More specifically, when the userpresses the enter button 9015, a display end instruction is issued tothe projector 91. Note that the operations for accepting selection of animage file by the user and displaying the selected image file can berepeated by repeating steps S204 to S208 bounded by the broken line inFIG. 12.

In step S209, the user removes the flash memory 93 from the USBconnector 9102. In step S210, the projector 91 clears a display imageprojected onto the screen 92 (or overwrites the image by a predeterminedimage such as a menu window) due to removal of the flash memory 93 instep S209. For example, in step S210 the connection request window shownin FIG. 13A is overwritten on an image displayed in steps S204 to S208.As a result, the projector 91 can prompt the user to connect the nextdevice. The user removes the flash memory 93 with the intention to endbrowsing of image files stored in the flash memory 93. Therefore, sincethe projector 91 clears an image displayed in steps S204 to S208, it canattain an image display operation according to the user's intention.

Note that patent reference 1 is known as a technique of clearing(overwriting) a display image by a predetermined image in step S210above. Patent reference 1 discloses a technique for clearing a displayimage at the end of a communication and a technique for clearing aprevious display image at the beginning of a communication.

A case will be exemplified below wherein another example of variousdevices to be connected is a digital camera. Note that a case will beexemplified below with reference to FIGS. 14A and 14B, and FIG. 15wherein a digital camera is connected to a printer, and the printeroutputs an image based on image data stored in that digital camera. As atypical example in this case, the CIPA DC-001-2003 standard (to bereferred to as “PictBridge” hereinafter) is available. In a method ofoutputting an image using this PictBridge, even a user unskilled inoperations of devices such as PCs can output an image using a printer byreadily operating a digital camera. An image output operation using thePictBridge will be described below.

FIG. 14A is a schematic view showing an overview when a digital camera94 is connected to a printer 96 to output an image. FIG. 14B is a blockdiagram showing the arrangement associated with a communication betweenthe printer 96 and digital camera 94. FIG. 15 is a sequence chartshowing the operation sequence when the digital camera 94 is connectedto the printer 96 to output an image.

As shown in FIG. 14A, the printer 96 has a discharge port 9601 and USBconnector 9602. The discharge port 9601 discharges a paper sheet 9603after image formation. To the USB connector 9602, the digital camera 94is connected via a USB cable 95. The digital camera 94 has a liquidcrystal panel screen 9401, operation member 9402, and PictBridge button9403. The liquid crystal panel screen 9401 displays a preview of animage or the like transferred via the PictBridge. The operation member9402 accepts an image selection instruction from the user. ThePictBridge button 9403 is a button which accepts an instruction to startPictBridge transfer from the user. An image based on image data storedin the digital camera 94 is output onto a paper sheet in the printer 96in such a manner that an image output instruction is output to theprinter 96 by an operation on the digital camera 94 side, and image datato be output is transmitted from the digital camera 94 to the printer96.

The operation sequence among the user, digital camera 94, and printer 96will be described below. As shown in FIG. 15, the operation sequence bythe user, digital camera 94, and printer 96 mainly includes steps S500to S509, which are executed in turn. In step S500, the user connects thedigital camera 94 and printer 96 via the USB cable 95. In step S501, aUSB communication is established based on the USB standard between thedigital camera 94 and printer 96 which are physically connected via theUSB cable 95. In this case, the printer 96 recognizes the digital camera94 as a capture device of Imaging Class based on the USB standard.

In step S502, a PictBridge connection is established between the digitalcamera 94 and printer 96. More specifically, a connection is establishedin a PTP (Picture Transfer Protocol) layer, device information isexchanged, and so forth. Then, a communication state as a PictBridgesequence transits to an idle state, and the printer 96 waits forissuance of a print job by the digital camera 94.

In step S503, the user issues a print instruction via the PictBridge byoperating the digital camera 94. More specifically, this printinstruction in step S503 is issued when the user presses the PictBridgebutton 9403. In step S504, the digital camera 94 transmits a PictBridgeprint job to the printer 96 based on the print instruction in step S503,and the printer 96 starts the operation of that print job.

In step S505, the printer 96 requests the digital camera 94 to transmitfile information to be printed in accordance with the print job in stepS504, and acquires that file information. Likewise, in step S506 theprinter 96 requests the digital camera 94 to transmit a file image(image data) to be printed in accordance with the print job in stepS504, and acquires that file image.

In step S507, the printer 96 executes decoding, scaling, printprocessing, and the like of an image indicated by the file acquired insteps S505 and S506, and outputs the paper sheet 9603 after imageformation from the discharge port 9601. In step S508, the printer 96notifies the digital camera 94 of an idle state upon completion of theprint job. Note that the operations for accepting selection of an imageto be printed from the user, and printing out the selected image can berepeated by repeating steps S503 to S508 bounded by the broken line inFIG. 15.

In step S509, the user removes the USB cable 95 from the printer 96 ordigital camera 94. Note that a device, which can control a communicationsession and logically disconnects a communication connection like thedigital camera 94, often disconnects a communication like closing of acommunication session in addition to a physical communicationdisconnection by, for example, removal of the USB cable 95. For example,when the battery remaining amount lowers during the aforementionedPictBridge sequence, the digital camera 94 side may execute control fordisconnecting a USB communication so as to reduce consumption power.

A communication disconnection on the digital camera 94 side will beexplained below by exemplifying the arrangement associated with acommunication between the digital camera 94 and printer 96. As shown inFIG. 14B, a USB host controller 9604 on the printer 96 side is connectedto a USB device controller 9407 on the digital camera 94 side via theUSB cable 95. The USB cable 95 includes four signal lines, that is, aVBUS line 9501, D+line 9502, D− line 9503, and GND line 9504.

The D+ line 9502 and D− line 9503 are used to transmit differentialsignals required to make a USB data communication, and also indicate adevice connection state by a voltage in a steady state. The D+ line 9502and D− line 9503 are respectively pulled down by resistors 9606 and 9605on the printer 96 side, and indicate a Low voltage when no USB cable isconnected. Thus, the printer 96 recognizes a USB non-connection state.On the other hand, when the printer 96 and digital camera 94 areconnected, the D+ line 9502 is pulled up by a resistor 9406 via a switch9405 on the digital camera 94 side. Then, when the switch 9405 is in aconnection state, the D+ line 9502 indicates a High voltage. As aresult, the printer 96 recognizes a USB connection state.

A CPU 9404 controls the switch 9405 on the digital camera 94 side. Notethat the CPU 9404 executes the following processing for the purpose of,for example, reducing consumption power of the digital camera 94. Forexample, in step S508 in which the PictBridge sequence transits to anidle state upon completion of the print job, the CPU 9404 controls theswitch 9405 on the digital camera 94 side to stop to pull up the D+ line9502. In this case, the D+ line 9502 indicates a Low voltage since it ispulled down on the printer 96 side. For this reason, the USB hostcontroller 9604 recognizes a USB non-connection state and disconnects aUSB communication, since this state is electrically equivalent to cableremoval in association with the D+ line 9502. That is, the communicationsession between the digital camera 94 and printer 96 is closed by thecontrol on the digital camera 94 side for the purpose of, for example,reducing consumption power.

When a communication disconnection is made on the digital camera 94side, as described above, the user meets the same behavior as that whenthe USB cable 95 is removed at the end of the print processing of theprinter 96. That is, the PictBridge sequence reaches the same state asthat when the process reaches step S509.

Note that the PictBridge that assumes printing has been exemplified, butthe PictBridge is applicable to a display on a display apparatus such asa projector or television. For example, when the digital camera 94 isconnected to the projector 91 to display an image, as shown in FIG. 16,the PictBridge allows the projector 91 to project and display an imagetransmitted from the digital camera 94 by a simple operation on thedigital camera 94 side. Like in the case in which the printer 96 anddigital camera 94 are connected, when a communication is disconnected onthe digital camera 94 side, the user meets the same behavior as thatwhen the USB cable 95 is removed. That is, the projector 91 clears animage which was transmitted from the digital camera 94 and was displayedimmediately before the communication disconnection by displaying, forexample, the connection request window.

As a technique for disconnecting a USB communication from the deviceside, patent reference 2 is known. Patent reference 2 discloses atechnique for disconnecting a communication by stopping to pull up adata line on the device side based on a disconnection instruction fromthe host side.

-   Patent Reference 1: Japanese Patent Laid-Open No. 7-123379-   Patent Reference 2: Japanese Patent Laid-Open No. 2006-235993

DISCLOSURE OF THE INVENTION Problems that the Invention is to Solve

As described above, the conventional display apparatus can be connectedto various devices, and can display image data stored in a connecteddevice. However, independently of the device class to be connected, whena communication is disconnected, the display operation of an imagetransmitted from that device ends. For this reason, in addition to theimage display end operation that the user intended by removing the flashmemory or USB cable, the image display operation often ends without theintention of the user by the control on the device side that logicallydisconnects a communication connection.

The present invention handles at least one of such conventionalproblems. That is, the present invention provides a display apparatus,which can control to continue or end a display operation according to adevice class when a communication connection with a device isdisconnected during execution of the display operation based on datatransmitted from the connected device, a control method thereof, and aprogram.

Means of Solving the Problems

According to the first invention of the present application, there isprovided a display apparatus characterized by comprising a display unit,a connection unit configured to connect an external device to be able tocommunicate with the external device, and a control unit configured tocontrol the display unit to make a display based on data received fromthe external device with which a communication connection is establishedvia the connection unit, characterized in that the control unit acquiresclass information indicating a class of the external device from theexternal device via the connection unit, controls the display unit tocontinue the display based on the data received from the external deviceat the time of disconnection of the communication connection with theexternal device if the class of the external device indicated by theclass information is a predetermined class, and controls the displayunit to end the display based on the data received from the externaldevice at the time of disconnection of the communication connection withthe external device if the class of the external device indicated by theclass information is not the predetermined class.

According to the second invention of the present application, there isprovided a control method of a display apparatus which comprises adisplay unit, a connection unit configured to connect an external deviceto be able to communicate with the external device, and a control unitconfigured to control the display unit to make a display based on datareceived from the external device with which a communication connectionis established via the connection unit, the method characterized bycomprising the control step of acquiring class information indicating aclass of the external device from the external device via the connectionunit, controlling the display unit to continue the display based on thedata received from the external device at the time of disconnection ofthe communication connection with the external device if the class ofthe external device indicated by the class information is apredetermined class, and controlling the display unit to end the displaybased on the data received from the external device at the time ofdisconnection of the communication connection with the external deviceif the class of the external device indicated by the class informationis not the predetermined class.

According to the third invention of the present application, there isprovided a display apparatus characterized by comprising a display unit,a connection unit configured to connect an external device to be able tocommunicate with the external device, and a control unit configured tocontrol the display unit to make a display based on data received fromthe external device with which a communication connection is establishedvia the connection unit, characterized in that the control unit acquiresclass information indicating a class of the external device from theexternal device via the connection unit, controls the display unit toend the display based on the data received from the external device atthe time of disconnection of the communication connection with theexternal device if the class of the external device indicated by theclass information is a predetermined class, and controls the displayunit to continue the display based on the data received from theexternal device at the time of disconnection of the communicationconnection with the external device if the class of the external deviceindicated by the class information is not the predetermined class.

According to the fourth invention of the present application, there isprovided a control method of a display apparatus which comprises adisplay unit, a connection unit configured to connect an external deviceto be able to communicate with the external device, and a control unitconfigured to control the display unit to make a display based on datareceived from the external device with which a communication connectionis established via the connection unit, the method characterized bycomprising the control step of acquiring class information indicating aclass of the external device from the external device via the connectionunit, controlling the display unit to end the display based on the datareceived from the external device at the time of disconnection of thecommunication connection with the external device if the class of theexternal device indicated by the class information is a predeterminedclass, and controlling the display unit to continue the display based onthe data received from the external device at the time of disconnectionof the communication connection with the external device if the class ofthe external device indicated by the class information is not thepredetermined class.

Effects of the Invention

According to the present invention, when a communication connection witha device is disconnected during execution of a display operation basedon data transmitted from the connected device, the display operation canbe controlled to continue or end according to the device class.

Other features and advantages of the present invention will becomeapparent from the following description taken in conjunction with theaccompanying drawings. Note that the same reference numerals denote thesame or similar components throughout the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate embodiments of the invention and,together with the description, serve to explain the principles of theinvention.

FIG. 1A is a view exemplifying a use mode of a display apparatusaccording to the present invention, that is, a schematic viewexemplifying a use mode upon connecting a flash memory to a displayapparatus to display an image;

FIG. 1B is a view exemplifying a use mode of the display apparatusaccording to the present invention, that is, a schematic viewexemplifying a use mode upon connecting a digital camera to the displayapparatus to display an image;

FIG. 2 is a block diagram illustrating the functional arrangement of thedisplay apparatus;

FIG. 3 is a schematic view exemplifying an input selection menu window;

FIG. 4A is a flowchart showing the processing of the display apparatus;

FIG. 4B1 is a flowchart showing the processing of the display apparatuswhen “Mass Storage Class” is determined in step S804 in FIG. 4A;

FIG. 4B2 is a flowchart showing the sequel of FIG. 4B1;

FIG. 4C1 is a flowchart showing the processing of the display apparatuswhen “Imaging Class” is determined in step S804 in FIG. 4A;

FIG. 4C2 is a flowchart showing the sequel of FIG. 4C1;

FIG. 5A is a schematic view showing an example of a projected displaywindow, that is, a schematic view exemplifying an input waiting window;

FIG. 5B is a schematic view showing an example of a projected displaywindow, that is, a schematic view exemplifying a display of image datafrom the digital camera;

FIG. 5C is a schematic view showing an example of a projected displaywindow, that is, a schematic view exemplifying an incompatibilitywindow;

FIG. 6A is a flowchart showing processing of the first modification(corresponding to FIG. 4C1) in the display apparatus;

FIG. 6B is a flowchart showing processing of the first modification(corresponding to FIG. 4C2) in the display apparatus;

FIG. 7 is a block diagram showing the peripheral arrangement of a CPUand USB connector 102 of the second modification in the displayapparatus;

FIG. 8A is a flowchart showing processing of the second modification(continued from any of FIGS. 8B1 to 8C2) in the display apparatus;

FIG. 8B1 is a flowchart showing processing of the second modification(corresponding to FIG. 4B1) in the display apparatus;

FIG. 8B2 is a flowchart showing processing of the second modification(corresponding to FIG. 4B2) in the display apparatus;

FIG. 8C1 is a flowchart showing processing of the second modification(corresponding to FIG. 4C1) in the display apparatus;

FIG. 8C2 is a flowchart showing processing of the second modification(corresponding to FIG. 4C2) in the display apparatus;

FIG. 9A is a flowchart showing processing of the third modification(corresponding to FIG. 8A) in the display apparatus;

FIG. 9B is a flowchart showing processing of the third modification(corresponding to FIG. 4A) in the display apparatus;

FIG. 10A is a flowchart showing processing of the fourth modification(corresponding to FIG. 9A) in the display apparatus;

FIG. 10B is a flowchart showing processing of the fourth modification(corresponding to FIG. 9B) in the display apparatus;

FIG. 11A is a schematic view showing an overview when a flash memory isconnected to a conventional projector to display an image;

FIG. 11B is a schematic view showing details of a control panel;

FIG. 12 is a sequence chart showing the operation sequence when theflash memory is connected to the projector to display an image;

FIG. 13A is a schematic view exemplifying a connection request windowprojected by the projector onto a screen;

FIG. 13B is a schematic view exemplifying a file selection windowprojected by the projector onto the screen;

FIG. 13C is a schematic view exemplifying a display of image data whichis stored in the flash memory, and is projected by the projector ontothe screen;

FIG. 14A is a schematic view showing an overview when a digital camerais connected to a printer to output an image;

FIG. 14B is a block diagram showing the arrangement associated with acommunication between the printer and digital camera;

FIG. 15 is a sequence chart showing the operation sequence when thedigital camera is connected to the printer to output an image; and

FIG. 16 is a schematic view showing an overview when a digital camera isconnected to a projector to display an image.

DESCRIPTION OF REFERENCE NUMERALS

-   -   1 . . . display apparatus    -   2 . . . screen    -   3 . . . flash memory    -   4 . . . digital camera    -   5 . . . USB cable

BEST MODE FOR CARRYING OUT THE INVENTION

An embodiment of the present invention will be described hereinafterwith reference to the drawings, but the present invention is not limitedto the embodiment to be described hereinafter. The embodiment of thepresent invention presents one aspect of the invention, and does notlimit the scope of the invention.

A use mode of a display apparatus according to the present inventionwill be described first with reference to FIGS. 1A and 1B whichexemplify the use modes of a display apparatus 1. As shown in FIG. 1A,as a use mode of the display apparatus 1, a flash memory 3 is connectedto a USB connector 102 of the display apparatus 1, and an image storedin the flash memory 3 is projected and displayed as an image 21 on ascreen 2. A control panel 101 includes various buttons used to acceptoperation instructions from the user. The user can browse image datastored in the flash memory 3 as the image 21 on the screen 2 by pluggingthe flash memory 3 into the USB connector 102 and operating the controlpanel 101.

Also, as shown in FIG. 1B, as another use mode, a digital camera 4 isconnected to the USB connector 102 of the display apparatus 1 via a USBcable 5, and an image stored in the digital camera 4 is projected anddisplayed as an image 22 on the screen 2. The digital camera 4 has aliquid crystal panel screen 401, operation member 402, and operationbutton 403. The liquid crystal panel screen 401 displays a preview of animage and the like to be transferred to the display apparatus 1. Theoperation member 402 accepts a selection instruction of an image fromthe user. The operation button 403 is a button used to accept a transferstart instruction to the display apparatus 1 from the user. A projectiondisplay operation by the display apparatus 1 based on image data storedin the digital camera 4 is attained in such a manner that an imagedisplay instruction by an operation on the digital camera 4 side isoutput from the digital camera 4 to the display apparatus 1, and imagedata to be output is transmitted from the digital camera 4 to thedisplay apparatus 1.

The user who uses the display apparatus 1 can appreciate an imagecaptured by the digital camera 4 by projecting and displaying it ontothe screen or can make a presentation for other users by projecting animage which is saved in the flash memory 3 and represents briefingpaper.

Details of the display apparatus 1 will be described below withreference to FIG. 2. FIG. 2 is a block diagram illustrating thefunctional arrangement of the display apparatus 1. As shown in FIG. 2, avideo signal is input to a video terminal 103 particularly via a videocable (not shown). The input video signal is converted into a digitalvideo signal by an AD converter 104 (Analog-To-Digital) connected to thevideo terminal 103. A CPU 107 (to be described later) sets samplingparameters (a frequency, phase, etc.) upon AD conversion. Note that whenan input video signal is a digital video signal, the AD converter 104 isnot required, and the present invention is applicable when anappropriate receiver is used as needed.

The converted digital video signal is input to a video processor 105connected to the AD converter 104. The video processor 105 applies videoadjustment processing such as resolution conversion processing, contrastadjustment, and brightness, sharpness, and gamma corrections, and OSDimage superimposing processing of a menu and the like. Note that “OSD”is an abbreviation for “On Screen Display”.

The CPU 107 controls the operation of the video processor 105.Furthermore, the video processor 105 can receive arbitrary image datafrom the CPU 107. For example, when the CPU 107 transmits image datareceived by a USB host controller 110 to the video processor 105, thevideo processor 105 can output that video as a video signal.

The video signal output from the video processor 105 is input to aliquid crystal driver 106, and is converted into signals (e.g., RGBvideo signals) suited to drive liquid crystal panels 117, 118, and 119.The liquid crystal panels 117, 118, and 119, which respectivelyrepresent three primary colors, that is, Red, Green, and Blue, includeliquid crystal pixels arranged in a matrix pattern, and form imagesbased on input signals. The liquid crystal panels 117, 118, and 119 arearranged to transmit light emitted from a lamp (not shown) through them,and modulate light coming from the lamp by images formed based on theinput signals.

A projection lens 120 projects and displays light modulated by theliquid crystal panels 117, 118, and 119 onto an external device (e.g.,the screen 2). The control panel 101 has an up arrow button, left arrowbutton, down arrow button, right arrow button, enter button, inputbutton, and power button as in the control panel 9101 that has beenexplained with reference to FIG. 11B. Pressing information of eachbutton on the control panel 101 is sent to the CPU 107 as an operationinstruction by the user. More specifically, that information is used tocontrol a cursor movement, an enter operation, and the like of a menu ona display window.

The USB host controller 110 is a circuit which makes a USB communicationwith an external device using a VBUS line 111, D+ line 112, D− line 113,and GND line 114, which are specified in the USB standard. In the USBhost controller 110, data to be transmitted/received is input/output bythe CPU 107. The D+ line 112 and D− line 113 are USB communication linesused to make a differential communication, and are respectively pulleddown by resistors 115 and 116. The VBUS line 111, D+ line 112, D− line113, and GND line 114 are connectable to an external device via the USBconnector 102 as a connection unit. The USB connector 102 serves as aUSB interface which can connect a USB device as an external device.Therefore, the display apparatus 1 and USB device can communicate witheach other via the USB connector 102.

The CPU 107 (Central Processing Unit) centrally controls the displayapparatus 1. More specifically, the CPU 107 manages to start up and shutdown the display apparatus 1, and controls the respective units such asthe AD converter 104, video processor 105, USB host controller 110, andliquid crystal driver 106. A ROM 108 (Read Only Memory) stores programcodes and various data required to operate the CPU 107. A CPU 107(Random Access Memory) provides a work area required to let the RAM 109operate.

The CPU 107 can select a video source to be displayed from the followingtwo sources in addition to the startup processing of respective blocksafter power-ON. The first video source is a video picture signal inputfrom the video terminal 103. The second video source is image datatransmitted from a device connected via the USB connector 102. The CPU107 controls the video processor 105 to project an input selection menuwindow in response to a user's operation on the control panel 101 as atrigger. FIG. 3 is a schematic view exemplifying the input selectionmenu window. As shown in FIG. 3, the input selection menu windowpresents a selection menu of “external video” and “USB” as a videosource to be displayed to the user.

After that, the CPU 107 receives a selection instruction input by auser's operation on the control panel 101, and executes a video sourceswitching operation. In this video source switching operation, when“USB” is selected, and the projection display operation of image datafrom the flash memory 3 or digital camera 4 connected to the displayapparatus 1 is to be executed, the CPU 107 sequentially executes theflowcharts including steps S801 to S832 exemplified in FIGS. 4A to 4C2.The processing of these flowcharts is executed until the power switch ofthe display apparatus 1 is turned off or until the input selection menuis displayed again, and “external video” is selected as a video source.

As shown in FIGS. 4A to 4C2, if the processing is started (S801), theCPU 107 controls the video processor 105 to project and display a USBdevice connection request window onto the screen 2 (S802). Thisconnection request window is as has been described with reference toFIG. 13A, and prompts the user to connect a USB device. The connectionrequest window is a kind of pattern image, and is displayed based onpattern image data stored in advance in the ROM 108.

The CPU 107 sends an inquiry to the USB host controller 110 to determinewhether or not a USB device is communication-connected via the USBconnector 102, and a USB communication is established (S803). If it isdetermined in step S803 that a USB communication is established, theprocess to be executed by the CPU 107 advances to the next step.

The CPU 107 sends an inquiry to the USB host controller 110 to determinea class of the communication-connected USB device (S804). This class isdetermined based on class information transmitted from the USB devicewhen the USB host controller 110 establishes a USB communication withthat USB device connected via the USB connector 102. More specifically,the class information of the USB device includes USB Mass Storage Classindicating the class of a device which is a simple storage andphysically disconnects a communication connection. Also, the classinformation includes USB Imaging Class (often also called ImagingDevice) indicating the class of a device which can execute communicationcontrol with the connected display apparatus 1 and can logicallydisconnect a communication connection depending on devices. Note thatUSB Mass Storage Class will be referred to as Mass Storage Class, andUSB Imaging Class will be referred to as Imaging Class hereinafter. Forexample, the flash memory 3 transmits class information indicating MassStorage Class to the display apparatus 1 at the time of connection, andthe digital camera 4 transmits class information indicating ImagingClass to the display apparatus 1 at the time of connection. If the classinformation indicates Mass Storage Class in step S804, the process to beexecuted by the CPU 107 advances to step S805; if the class informationindicates Imaging Class, the process advances to step S817; otherwise,the process advances to step S831.

FIG. 4A shows “Mass Storage Class” and “Imaging Class” as the deviceclasses, but the present invention is not limited to these classes. Forexample, the display apparatus 1 may store a class for which an imagedisplay operation is to be continued and a class for which the operationis to be ended (or one of these classes) at the time of disconnection ofa communication.

The CPU 107 executes a sequence of steps S805 to S816 when thecommunication-connected USB device is a USB mass storage such as theflash memory 3. In step S805, the CPU 107 reads out directory entryinformation stored in the USB device via the USB host controller 110.

In step S806, the CPU 107 sends an inquiry to the USB host controller110 to determine whether or not a USB communication with the USB devicewas disconnected in the previous process (step S805 in this case). If itis determined in step S806 that the USB communication was disconnected,the process to be executed by the CPU 107 returns to step S802.

In step S807, the CPU 107 controls the video processor 105 to display afile selection window that enumerates image file names based on thereadout directory entry information. This file selection window is ashas been described with reference to FIG. 13B, and is a window thatdisplays a file name list of image files stored in the flash memory 3and a cursor used to select them. The display apparatus 1 prompts theuser to select an image file to be displayed of those stored in theflash memory 3 using this file selection window.

The CPU 107 determines in step S808 whether or not a USB communicationwith the USB device was disconnected, as in step S806. The CPU 107determines in step S809 whether or not the user has made an operation onthe control panel 101. If it is determined in step S809 that the userhas not made any operation, the process to be executed by the CPU 107returns to step S808.

In step S810, the CPU 107 updates the file selection window based on theuser's operation on the control panel 101. More specifically, when theuser presses the up or down arrow button on the control panel 101, theCPU 107 reconfigures and displays a window on which the cursor to berendered to select a file of interest has been moved.

The CPU 107 determines in step S811 based on a user's operation on thecontrol panel 101 whether or not the user has made an operation toselect an image file to be displayed. More specifically, when the userpresses the enter button on the control panel 101, the CPU 107determines that an image file in a cursor line is determined as that tobe displayed. If no image file selection operation is made, the processto be executed by the CPU 107 returns to step S808.

In step S812, the CPU 107 reads out a file image of the image fileselected in step S811 from the USB device via the USB host controller110. The CPU 107 determines in step S813 whether or not a USBcommunication with the USB device was disconnected, as in step S806.

In step S814, the CPU 107 controls the video processor 105 to projectand display an image based on the readout file image on the screen 2,after the image is scaled to match the resolution of the liquid crystalpanels 117, 118, and 119. The image which is projected and displayed onthe screen 2 is the same as that which has been described with referenceto FIG. 13C, and is based on image data stored in advance in the flashmemory 3.

The CPU 107 determines in step S815 whether or not a USB communicationwith the USB device was disconnected, as in step S806. The CPU 107determines in step S816 based on a user's operation on the control panel101 whether or not the user gives the instruction to end the imagedisplay operation. More specifically, the CPU 107 makes thisdetermination by acquiring pressing information of the enter button onthe control panel 101. If the user does not give the instruction to endthe image display operation, the process to be executed by the CPU 107returns to step S815. If the user gives the instruction to end the imagedisplay operation, the process to be executed by the CPU 107 returns tostep S807, and the file selection window is displayed again to promptthe user to select another image file.

On the other hand, the CPU 107 executes a sequence of steps S817 to S830when the connected USB device corresponds to, for example, Imaging Classsuch as the digital camera 4 compatible to the PictBridge. Note that thePictBridge-compatible digital camera 4 will be exemplified below, and acase will be described wherein the scheme of the PictBridge is diverted,and the projection display operation of the display apparatus 1 is madeusing a print instruction (image output) from the digital camera 4. Instep S817, the CPU 107 executes PictBridge connection processing withrespect to the USB device via the USB host controller 110. Note thatthis processing corresponds to step S502, which has been explained withreference to FIG. 15.

In step S818, the CPU 107 sends an inquiry to the USB host controller110 to determine whether or not a USB communication with the USB devicewas disconnected in the previous process (step S817 in this case). If itis determined in step S818 that the USB communication was disconnected,the process to be executed by the CPU 107 advances to step S830.

The CPU 107 determines in step S819 whether or not the PictBridgeconnection processing in step S817 has succeeded, and a PictBridgeconnection is established. If a PictBridge connection is not establishedbecause, for example, the USB device to be connected is incompatible tothe PictBridge, the process to be executed by the CPU 107 advances tostep S831.

In step S820, the CPU 107 controls the video processor 105 to projectand display an input waiting window. This input waiting window is awindow used to prompt the user to print an image file (or to transfer animage to a projector) by the PictBridge function from the digital cameraside, as shown in FIG. 5A. Note that this step S820 corresponds to anidle state in which the control waits for a “print” instruction in stepS503 described with reference to FIG. 15.

The CPU 107 determines in step S821 whether or not a USB communicationwith the USB device was disconnected, as in step S818. The CPU 107determines in step S822 whether or not a print job start communicationis made from the USB device via the USB host controller 110. Thiscommunication corresponds to step S504 which has been explained withreference to FIG. 15. If it is determined in step S822 that no startinstruction is issued, the process to be executed by the CPU 107 returnsto step S821.

The CPU 107 determines in step S823 whether or not a USB communicationwith the USB device was disconnected, as in step S818. In step S824, theCPU 107 acquires information of an image file to be output included inthe print job from the USB device via the USB host controller 110. Thisstep S824 corresponds to step S505 which has been described withreference to FIG. 15.

The CPU 107 determines in step S825 whether or not a USB communicationwith the USB device was disconnected, as in step S818. In step S826, theCPU 107 acquires an image of the image file included in the print jobfrom the USB device via the USB host controller 110. This step S826corresponds to step S506 which has been described with reference to FIG.15.

The CPU 107 determines in step S827 whether or not a USB communicationwith the USB device was disconnected, as in step S818. In step S828, theCPU 107 controls the video processor 105 to project and display theacquired image on the screen 2, after the image is scaled to match theresolution of the liquid crystal panels 117, 118, and 119. The image,which is projected and displayed on the screen 2, is an image based onimage data captured by the digital camera, and is an image of a personor the like, as shown in, for example, FIG. 5B.

In step S829, the CPU 107 notifies the USB device, via the USB hostcontroller 110, that a communication state based on the PictBridgeconnection transits to an idle state. This notification in step S829corresponds to step S508 which has been described with reference to FIG.15.

If it is determined in step S818, S821, S823, S825, or S827 that the USBcommunication was disconnected, the process of the CPU 107 advances tostep S830. The CPU 107 determines in step S830 whether or not theprojection display operation of an image based on the image acquiredfrom the USB device is in progress (i.e., whether or not the process haspassed step S828). If the projection display operation of the image isin progress, the process of the CPU 107 returns to step S803; otherwise,the process of the CPU 107 returns to step S802.

On the other hand, if an incompatible device class is determined in stepS804, or if it is determined in step S819 that a PictBridge connectionis not established, the process of the CPU 107 advances to step S831. Instep S831, the CPU 107 controls to project and display anincompatibility window. This incompatibility window is a window used tonotify the user that the connected USB device is incompatible to thedisplay apparatus 1, as shown in FIG. 5C.

In step S832, the CPU 107 sends an inquiry to the USB host controller110 to determine whether or not a USB communication with the USB devicewas disconnected. This determination in step S832 continues until theUSB communication is disconnected, and if the USB communication isdisconnected, the process of the CPU 107 returns to step S802.

As described above, when a USB communication is disconnected while thedisplay apparatus 1 is connected to a USB device such as a flash memorydevice, and executes the projection display operation of image datastored in that device, the display apparatus 1 overwrites an image whoseprojection display operation is in progress by the connection requestwindow (S802). When the class of the connected device corresponds to,for example, the flash memory device, the USB connection is disconnectedmainly by removal of the device by the user. Furthermore, the userremoves the device with the intention to end the projection displayoperation. Hence, when the USB connection is disconnected, it ispreferable for the display apparatus 1 to overwrite an image, whoseprojection display operation is in progress, by the connection requestwindow without continuing the projection display operation.

On the other hand, when a USB connection is disconnected while thedisplay apparatus 1 is connected to a USB device such as a digitalcamera, and executes the projection display operation of image datastored in that device, the display apparatus 1 continues to display theimage, whose projection display operation is in progress, without beingoverwritten by the connection request window (transition from step S830to step S803). When the class of the connected device corresponds to,for example, the digital camera, the USB communication may bedisconnected either by removal of the device by the user or by controlon the USB device side. Therefore, since the USB connection isdisconnected by not only removal of the device by the user who intendedto end the projection display operation, it is preferable for thedisplay apparatus 1 to continue to display an image, whose projectiondisplay operation is in progress, when the USB connection isdisconnected.

That is, when a communication is disconnected while the displayapparatus 1 executes the projection display operation based on imagedata from the connected device, the display apparatus 1 controls whetheror not to continue the display operation of the image whose projectiondisplay operation is in progress according to the class of the connecteddevice. Therefore, the display apparatus 1 can eliminate the opportunityof a display state which is likely to occur depending on the class ofthe connected device and is not intended by the user. For example, thedisplay apparatus 1 can eliminate occurrence of situations that theimage display operation is unwantedly ended in a case in which the userintends to browse images and that the image display operation isunwantedly continued in a case in which the user intends to end imagebrowsing. Note that, in this embodiment, the image of the connectionrequest window is used as an overwrite image. Alternatively, forexample, a solid black or blue-back pattern image may be used.

[First Modification]

As the first modification of the aforementioned embodiment, a case willbe described wherein the processes of FIGS. 4C1 and 4C2 of those to beexecuted by the CPU 107 of the display apparatus 1 exemplified in FIGS.4A to 4C2 are modified like the flowcharts shown in FIGS. 6A and 6B.Note that the same step numbers denote the same processes, and arepetitive description thereof will be avoided.

As shown in FIGS. 6A and 6B, in the first modification, steps S818,S823, S825, and S827 in the sequence of the CPU 107 exemplified in FIGS.4C1 and 4C2 are respectively replaced by steps S1318, S1323, S1325, andS1327.

In step S1318, the CPU 107 sends an inquiry to the USB host controller110 to determine whether or not a USB communication with the USB devicewas disconnected in the previous process (step S817 in this case). If itis determined in step S1318 that the USB communication was disconnected,the process to be executed by the CPU 107 returns to step S802. Notethat the processing contents in steps S1323, S1325, and S1327 are thesame as in step S1318.

In step S821, the CPU 107 sends an inquiry to the USB host controller110 to determine whether or not a USB communication with the USB devicewas disconnected in the previous process (step S820 in this case). If itis determined in step S821 that the USB communication was disconnected,the process to be executed by the CPU 107 advances to step S830. Thatis, when the USB communication is disconnected at the display timing ofthe input waiting window, and in an idle state of the communication,since the process of the CPU 107 temporarily advances to step S830, animage can be prevented from being immediately overwritten by theconnection request window.

As described above, in the first modification, the following processesof the display apparatus 1 executed when a communication is disconnectedwhile the display apparatus 1 is connected to the PictBridge-compatibledevice and executes the projection display operation of an image storedin that device are different from the aforementioned embodiment. Whenthe PictBridge connection is not in an idle state, that is, acommunication is underway at the time of the aforementionedcommunication disconnection, the display apparatus 1 overwrites an imagewhose projection display operation is in progress by the connectionrequest window. When the PictBridge connection is in an idle state, thatis, a communication is not underway, an image whose projection displayoperation is in progress is continuously displayed.

When the PictBridge connection is in a non-idle state, that is, acommunication is underway, a USB communication is more likely to bedisconnected at that time not by control on the USB device side but by,for example, removal of the USB device by the user. Therefore, when acommunication is disconnected during the USB communication, it ispreferable for the display apparatus 1 to overwrite an image, whoseprojection display operation is in progress, by the connection requestwindow without continuously displaying the image. When a communicationis disconnected while the USB communication is in an idle state, suchdisconnection may be caused either by removal of the USB device by theuser or by control on the USB device side. Therefore, since a USBcommunication in an idle state is disconnected by not only removal ofthe device by the user who intends to end the projection displayoperation, it is preferable for the display apparatus 1 to continue todisplay an image whose projection display operation is in progress.

[Second Modification]

The second modification of the aforementioned embodiment will bedescribed below. In the second modification, the peripheral arrangementof the CPU 107 and USB connector 102 of the display apparatus 1exemplified in FIG. 2 is modified, as shown in FIG. 7. Also, in thesecond modification, the processes to be executed by the CPU 107 of thedisplay apparatus 1 exemplified in FIGS. 4B1 to 4C2 are modified, asshown in the flowcharts shown in FIGS. 8A to 8C2. Note that the samereference numerals denote the same components, and a repetitivedescription thereof will be avoided.

As shown in FIG. 7, the display apparatus 1 includes an insertiondetector 121 which detects insertion of a USB plug in the USB connector102. In the insertion detector 121, a conductive terminal 1212 having aprojection 1211, which is arranged at a position where the projection1211 physically interferes with a USB plug, and a grounded conductiveterminal 1213 are arranged in the USB connector 102 to be brought intocontact with each other when a USB plug is not inserted. The conductiveterminal 1212 is pulled up by a resistor 122, and is connected to aninput port of the CPU 107.

Therefore, in the insertion detector 121, when a USB plug is insertedinto the USB connector 102, the USB plug pushes up the conductiveterminal 1212, and the conductive terminals 1212 and 1213 are open.Hence, the CPU 107 can recognize insertion/removal of the USB plugto/from the USB connector 102.

In the second modification, steps S806, S808, S813, S815, S818, S821,S823, S825, and S827 shown in FIGS. 4B1 to 4C2 are changed, as shown inFIGS. 8B1 to 8C2, and FIG. 8A having steps S1530 and S1533 is added.

In step S1506, the CPU 107 sends an inquiry to the USB host controller110 to determine whether or not a USB communication with the USB devicewas disconnected in the previous process (step S805 in this case). If itis determined in step S1506 that the USB communication was disconnected,the process to be executed by the CPU 107 advances to step S1530. Notethat the processing contents in steps S1508, S1513, S1515, S1518, S1521,S1523, S1525, and S1527 are the same as in step S1506.

The CPU 107 determines in step S1530 whether or not the projectiondisplay operation of an image based on image data acquired from the USBdevice is in progress (that is, whether or not the process has passedstep S814 or S828). If the projection display operation of the image isin progress, the process of the CPU 107 advances to step S1533;otherwise, the process of the CPU 107 returns to step S802.

The CPU 107 determines in step S1533 using the insertion detector 121whether or not a USB plug is physically removed from the USB connector102. If it is determined in step S1533 that the USB plug is physicallyremoved, the process of the CPU 107 returns to step S802. On the otherhand, if it is determined that the USB plug is not physically removed,the process of the CPU 107 returns to step S803.

As described above, in the second modification, when the USB plug isphysically removed and a USB communication is disconnected during theprojection display operation of image data stored in the connected USBdevice, the display apparatus 1 overwrites the image whose projectiondisplay operation is in progress by the connection request window. Notethat when a USB communication is disconnected not by physical removal ofthe USB plug, the display apparatus 1 does not overwrite the image whoseprojection display operation is in progress by the connection requestwindow. Thus, the display apparatus 1 can eliminate occurrence ofsituations that the image display operation is unwantedly ended in acase in which the user intends to browse images and that the imagedisplay operation is unwantedly continued in a case in which the userintends to end image browsing.

[Third Modification]

The third modification, which further modifies the processing of theaforementioned second modification, will be described below withreference to the flowcharts shown in FIGS. 9A and 9B. Note that the samestep numbers denote the same processes, and a repetitive descriptionthereof will be avoided. As shown in FIGS. 9A and 9B, in the thirdmodification, step S1533 is replaced by step S1633 in the sequence ofthe CPU 107 exemplified in FIG. 8A (FIG. 9A), and steps S1634 to S1636are added in the sequence of the CPU 107 exemplified in FIG. 4A (FIG.9B).

The CPU 107 determines in step S1633 using the insertion detector 121whether or not a USB plug is physically removed from the USB connector102. If it is determined in step S1633 that the USB plug is physicallyremoved, the process of the CPU 107 returns to step S802. On the otherhand, if it is determined that the USB plug is not physically removed,the process of the CPU 107 advances to step S1634.

In step S1634, the CPU 107 sets and starts a timer which performs acount-down operation for a predetermined period (second period)specified in advance in the ROM or the like. If the CPU 107 determinesin step S1635 that the timer started in step S1634 reaches a time-out,or the user issues an instruction on the control panel 101, the processreturns to step S802.

In step S1636, the CPU 107 sends an inquiry to the USB host controller110 to determine whether or not the USB device is connected, and a USBcommunication is established. If it is determined in step S1636 that theUSB communication is established, the process of the CPU 107 advances tostep S804. On the other hand, if it is determined that the USBcommunication is not established, the process of the CPU 107 returns tostep S1635. Therefore, in steps S1634 to S1636, the processing waitsbefore the user issues an instruction or the second period set by thetimer elapses until the USB communication is established.

As described above, in the third modification, when the USB plug isphysically removed and the USB communication is disconnected while theprojection display operation of image data stored in the connected USBdevice is in progress, the display apparatus 1 overwrites the imagewhose projection display operation is in progress by the connectionrequest window. On the other hand, when it is determined that the USBplug is not physically removed, the image whose projection displayoperation is in progress is not overwritten by the connection requestwindow until the second period elapses or the user issues aninstruction. Hence, the display apparatus 1 can eliminate occurrence ofsituations that the image display operation is unwantedly ended in acase in which the user intends to browse images and that the imagedisplay operation is unwantedly continued in a case in which the userintends to end image browsing.

[Fourth Modification]

The fourth modification that further modifies the aforementioned thirdmodification will be described below with reference to the flowchartsshown in FIGS. 10A and 10B. Note that the same step numbers denote thesame processes, and a repetitive description thereof will be avoided. Asshown in FIGS. 10A and 10B, in the fourth modification, step S1633 isreplaced by step S1733 in the sequence of the CPU 107 exemplified inFIG. 9A (FIG. 10A), and step S1737 is added to the sequence of the CPU107 exemplified in FIG. 9B (FIG. 10B).

The CPU 107 determines in step S1733 using the insertion detector 121whether or not a USB plug is physically removed from the USB connector102. If it is determined in step S1733 that the USB plug is physicallyremoved, the process of the CPU 107 advances to step S1737. On the otherhand, if it is determined that the USB plug is not physically removed,the process of the CPU 107 advances to step S1634.

In step S1737, the CPU 107 sets and starts a timer which performs acount-down operation for a predetermined period (first period) which isset in advance in the ROM or the like, and is shorter than the secondperiod set in step S1634.

As described above, in the fourth modification, when the USB plug isphysically removed, and a USB communication is disconnected while theprojection display operation of image data stored in the connected USBdevice is in progress, the display apparatus 1 overwrites the imagewhose projection display operation is in progress by the connectionrequest window. The connection request window is overwritten when thefirst period set to be shorter than the second period elapses or whenthe user issues an instruction. On the other hand, when it is determinedthat the USB plug is not physically removed, the image whose projectiondisplay operation is in progress is not overwritten by the connectionrequest window until the second period set to be longer than the firstperiod elapses or the user issues an instruction.

Note that the description of the aforementioned embodiment is merely anexample, and the present invention is not limited to this. Thearrangement and operation in the aforementioned embodiment can bemodified as needed. For example, the projector has been exemplified asthe display apparatus in this embodiment, but a PDP, LCD, SED, CRTmonitor, and the like may be used. Note that “PDP” is an abbreviationfor “Plasma Display Panel”. Also, “LCD” is an abbreviation for “LiquidCrystal Display”. “SED” is an abbreviation for “Surface-ConductionElectron-emitter Display”. Furthermore, “CRT” is an abbreviation for“Cathode Ray Tube”.

This embodiment has exemplified the arrangement using USB, but thepresent invention is not particularly limited to this. For example, anSDIO (Secure Digital Input/Output) interface and other interfaces may beused. Furthermore, as an external storage device using a USB massstorage, an SD (Secure Digital) card memory, CF card, and the like maybe used.

In the second, third, and fourth modifications, the insertion detector121, which is a mechanism for detecting a physical contact of theconnector, is used as means for detecting a physical connection of theUSB plug, but the detection mechanism is not particularly limited. Forexample, as another means for detecting a physical connection of the USBplug, a current amount that flows through the VBUS line may be measured,and if the measured current amount exceeds a predetermined value, it maybe determined that the USB plug is physically connected.

Other Embodiments

The aforementioned embodiments can be implemented in a software mannerby a computer (or a CPU, MPU, etc.) of a system or apparatus. Therefore,a computer program itself supplied to the computer to implement theaforementioned embodiments using the computer implements the presentinvention. That is, the computer program itself required to implementthe functions of the aforementioned embodiments is one invention of thepresent invention.

Note that the form of the computer program required to implement theaforementioned embodiments is not particularly limited as long as thatprogram is computer-readable. For example, the program may adopt theforms of an object code, a program to be executed by an interpreter,script data to be supplied to an OS, and the like, but the presentinvention is not limited to them. The computer program required toimplement the aforementioned embodiments is supplied to the computer viaa storage medium or wired/wireless communications. As the storage mediumfor supplying the program, for example, magnetic storage media such as aflexible disk, hard disk, and magnetic tape, optical/magneto-opticalstorage media such as an MO, CD, and DVD, a nonvolatile semiconductormemory, and so forth may be used.

As a computer program supply method using the wired/wirelesscommunications, a method using a server on a computer network isavailable. In this case, a server stores a data file (program file) thatcan be a computer program which forms the present invention. The programfile may be either an executable format file or source codes. Then, theprogram file is supplied by downloading to a client computer that hasaccessed the server. In this case, the program file may be segmentedinto a plurality of segment files, which may be allocated on differentservers. That is, the server which provides the program file required toimplement the aforementioned embodiments to the client computer is alsoone invention of the present invention.

Also, a storage medium, which stores the encrypted program required toimplement the aforementioned embodiments, may be delivered, and keyinformation required to decrypt the encrypted program may be supplied tothe user who meets a predetermined condition, so as to allow that userto install the program on a computer of the user. The key informationcan be supplied to the user by making him or her download it from ahomepage via, for example, the Internet. The computer program requiredto implement the aforementioned embodiments may use the functions of anOS which already runs on the computer. Furthermore, some functions ofthe computer program required to implement the aforementionedembodiments may be configured by firmware which runs on an expansionboard or the like attached to the computer, or may be executed by a CPUequipped on the expansion board or the like.

The present invention is not limited to the above embodiments andvarious changes and modifications can be made within the spirit andscope of the present invention. Therefore, to apprise the public of thescope of the present invention, the following claims are appended.

This application claims the benefit of Japanese Patent Application No.2008-141678, filed May 29, 2008, which is hereby incorporated byreference herein in its entirety.

1-14. (canceled)
 15. A display control apparatus comprising: acommunication unit configured to communicate with an external device;and a display control unit configured to display, on a display unit, animage received from the external device via the communication unit, andif communication with the external device is disconnected, to stop thedisplay of the image received from the external device, wherein thedisplay control unit varies a period of time from the disconnection tothe stopping of the display of the image depending on a type of theexternal device.
 16. The display control apparatus according to claim15, wherein the display control unit stops the display of the imageimmediately or after a specific period of time elapses from thedisconnection depending on a type of the external device.
 17. Thedisplay control apparatus according to claim 15, wherein if thecommunication with the external device is physically disconnected, thedisplay control unit stops the display of the image after apredetermined first period of time elapses.
 18. The display controlapparatus according to claim 17, wherein if the communication with theexternal device is logically disconnected, the display control unitstops the display of the image after a predetermined second period oftime elapses, the predetermined second period of time being longer thanthe predetermined first period of time.
 19. The display controlapparatus according to claim 15, wherein the communication unit isconnected with the external device via a physical communicationinterface.
 20. The display control apparatus according to claim 15,wherein the display unit has a lens for projecting an image.
 21. Adisplay control apparatus comprising: a communication unit configured tocommunicate with an external device; and a display control unitconfigured to display, on a display unit, an image received from theexternal device via the communication unit, and if communication withthe external device is disconnected, to stop the display of the imagereceived from the external device, wherein the display control unitvaries a period of time from the disconnection to the stopping of thedisplay of the image depending on a determination result as to whetherthe disconnection of the communication with the external device is aphysical disconnection or a logical disconnection.
 22. The displaycontrol apparatus according to claim 21, wherein the display controlunit stops the display of the image immediately or after a specificperiod of time elapses from the disconnection depending on adetermination result as to whether the disconnection of thecommunication with the external device is a physical disconnection or alogical disconnection.
 23. The display control apparatus according toclaim 21, wherein if the communication with the external device isphysically disconnected, the display control unit stops the display ofthe image after a predetermined first period of time elapses.
 24. Thedisplay control apparatus according to claim 23, wherein if thecommunication with the external device is logically disconnected, thedisplay control unit stops the display of the image after apredetermined second period of time elapses, the predetermined secondperiod of time being longer than the predetermined first period of time.25. The display control apparatus according to claim 21, wherein thecommunication unit is connected with the external device via a physicalcommunication interface.
 26. The display control apparatus according toclaim 21, wherein the display unit has a lens for projecting an image.27. A control method of a display control apparatus having acommunication unit configured to communicate with an external device,the method comprising: a display control step of displaying, on adisplay unit, an image received from the external device via thecommunication unit, and if communication with the external device isdisconnected, stopping the display of the image received from theexternal device, wherein the display control step varies a period oftime from the disconnection to the stopping of the display of the imagedepending on a type of the external device.
 28. A control method of adisplay control apparatus having a communication unit configured tocommunicate with an external device, the method comprising: a displaycontrol step of displaying, on a display unit, an image received fromthe external device via the communication unit, and if communicationwith the external device is disconnected, stopping the display of theimage received from the external device, wherein the display controlstep varies a period of time from the disconnection to the stopping ofthe display of the image depending on a determination result as towhether the disconnection of the communication with the external deviceis a physical disconnection or a logical disconnection.